ABSTRACT Our current AHRQ T32 program has successfully recruited diverse fellows and prepared them for health services research careers. We have trained 13 researchers, resulting in 29 presentations and 30 publications. Nine have graduated, with 7 obtaining academic appointments, and two still completing their PhD training. This competitive renewal capitalizes on the opportunity to train fellows in an environment of innovation and transformation, as Boston Medical Center (BMC) transitions to its own Accountable Care Organization and becomes a Learning Health System. Over the past year, BMC, New England?s largest safety-net hospital, has become the epicenter of the Boston Accountable Care Organization (BACO). BACO is projected to be responsible for 185,000 covered lives, making it an ideal setting in which to train researchers. Our interdisciplinary predoctoral and postdoctoral fellowship aims to produce Family Medicine, General Internal Medicine, Pediatrics, and Public Health researchers who will lead efforts to improve health care delivery for underserved patients. The four objectives of our program are to: (1) Recruit and retain high-quality, diverse candidates interested in research careers focused on improving health care quality, access, and delivery for underserved patients; (2) Provide predoctoral and postdoctoral fellows with comprehensive research training; (3) Produce graduates who will conduct research on health care quality, access and delivery for low-income populations and whose research translates to systems change; and (4) Evaluate our program for continuous improvement. The program is led by Dr. Megan Bair-Merritt, an experienced researcher and mentor, and Co-Directed by an interdisciplinary team of senior scientists. We have established four pedagogical structures essential to training research fellows: (1) Intensive mentoring; (2) Boston University School of Public Health (BUSPH) courses culminating in a Master?s in Health Services Research for postdoctoral fellows and a PhD for predoctoral fellows; (3) Interdisciplinary academic seminars; and (4) Supervised conduct of at least two research projects. In this competitive renewal, we have added to each structured learning, including: pairing trainees with traditional research mentors and a hospital leadership mentor; training in quality improvement and implementation science; and the conduct of at least one research project leveraging clinical data to address a health delivery question. Predoctoral training includes the first 3 didactic years of the PhD program. Postdoctoral training is 2 years. Each year, we will train 3 predoctoral and 3 postdoctoral fellows. Fellows will become health service researchers focused on health care quality, delivery, and outcomes for low-income populations. We track graduates 1, 5, and 10 years after graduation (goal: >85% enter research careers focused on improving healthcare quality; >70% remain in health services research after 3 years; >50% lead efforts to implement new care models and have >1 funded research within 5 years).